Process of making vinyl resin plastic sponge



N0V- 25, 1958 P. v. BuTscH 2,861,963

PROCESS OF' MAKING VINYL RESIN PLASTIC SPONGE Filed July 3, 1957 ff/APE77/5 F50/77 Byzmjoy A. GENT United States Patent() PROCESS oF MAKINGVINYL REsm PLASTIC sPoNGE Application July 3, 1957, Serial No. 669,798

6 Claims. (Cl. 26Q-2.5)

This invention relates to a process of making a plasticized vinyl resinsponge. More particularly it relates to a process of making a producthaving a cellular structure resembling somewhat that of latex Vfoamrubber which, as is well-known, is made by beating air into rubber latexto which a sensitizing agent and vulcanizng and compounding ingredientshave been added, followed` by shaping and vulcanization.

This application isa continuation-in-part of my copendiug applicationSerial No. 436,540, led June 14, 1954, now abandoned.

The principal object of the present invention is to provide a simple,commercially feasible, and highly effective process of making aplasticized vinyl resin sponge which obviates the necessity for externalgassing with an inert gas such as carbon dioxide, and which avoids thenecessity of using a chemical blowing agent with the attendantcomplication and expense. Another object is to provide such a processwhich yields a soft foamed product having excellent physical propertiesand characterized by low specific gravity or density and bybreathability similar to that of latex foam rubber. Another object is toprovide such a process wherein ordinary air is simply incorporated intothe original mobile or fluent mixture by mechanical frothing in the sameway as that by which air is incorporated into the aforementioned rubberlatex composition in the manufacture of latex foam rubber. Numerousother objects will more fully hereinafter appear.

The accompanying drawing, which is self-explanatory, portraysdiagrammatically the manufacture of plasticized vinyl resin sponge inaccordance with my invention.

I have discovered that plasticized vinyl resin sponge having verydesirable physical properties can easily and economically bemanufactured by mechanically frothing an intimate mixture comprising aplastsol of a particulate thermoplastic vinyl resin selected from thegroup consisting of polyvinyl chloride and copolymers of a majorproportion of vinyl chloride and a minor proportion of a copolymerizablemonomer, and a high-boiling organic liquid plasticizer for the resin, anon-ionic surface-active agent, an alkali metal salt of a sulfonatedfatty alcohol, and an alkali metal salt of ethylene diamine tetraaceticacid, whereby the surrounding gas is incorporated in and retained by themixture, subsequently heating the resulting froth at a temperature andfor a time sufficient to fuse theresin particles with the plasticizerwhile maintaining the froth structure, and cooling the resultingmaterial to room temperature.

My experiments have shown that it is necessary to use the threeaforementioned ingredients, namely the non-ionic surface-active agent,the alkali metal salt of a sulfonated fatty alcohol, and the alkalimetal salt of ethylene diamine tetraacetic acid, in combination, inconjunction with the plastsol in onder to obtain a product having asuciently low density. If any one of these three materials is omitted,the density of the product 4 -ice becomes excessively high. Apparentlythese three materials cooperate in some Way to bring about new andunexpected results, namely the retention of the froth structure duringthe heating which is done to effect fusion of the resin and theplasticizer.

In practicing my invention, I can use any conventional plastisol. As isWell-known, plastisols are fluent mixtures of particulate vinyl resinsand high-boiling organic liquid plasticizers therefor which aresubstantially non-solvents for the resin at ordinary temperatures, i.e., not over 100 F., but are capable of dissolving the resin at elevatedtemperatures above 100 F.

and more commonly ranging from 300 to 350 F., to-

form a single phase material, sometimes referred to as a gel, which4upon cooling to room temperature yields a product which is solid andhas good strength.`

The vinyl resin of the plastsol can be any of the conventionalthermoplastic, normally solid, vinyl resins commonly used in makingplastisols. It may be either polyvinyl chloride or a copolymer of amajor proportion of vinyl chloride and a minor proportion of acopolymerzable monomer which may be vinyl acetate, vinylidene chloride,diethyl maleate, diethyl fumarate, etc., the relative proportions ofcombined monomers usually being equal to -95% vinyl chloride and l5-5%copolymerizable monomer.

Any of the conventional high-boiling organic 4liquid plasticizerscommonly used in making plastisols can be employed in practicing myinvention. The plasticizer should be substantially a non-solvent for theresin at temperatures not over F. so that no fusion takes place untilduring the step of heating the frothed mixture. The plasticizer shouldbe capable of dissolving the resin at moderately elevated temperatures,say at 300-350 F. The plastsol grade resin is mixed with the plasticizerto form a paste-like dispersion with which the other three ingredientsand any desired additional components such as coloring material,fillers, stabilizers for the resin, etc. are incorporated. So far as Ihave been able to determine, the order of incorporating the severalingredients to form the uent mixture subjected to frothing isimmaterial.

The plasticizer is usually an ester, ether, or ketone or a mixture oftwo or more compounds of this type. Examples are tricresyl phosphate,octyl diphenyl phosphate, dibutyl phthalate, dioctyl phthalate, dibutylsebacate, dioctyl sebacate, butyl phthalyl, butyl glycolate, linearpolyester resin plasticizers such as are disclosed at Industrial andEngineering Chemistry, 37,504 (1945) e. g., Paraplex G-50 manufacturedby Rohm and Haas, and plasticizers made by introducing epoxy groups intoa drying oil, e. g., soy bean oil, an example of the latter type ofplasticizer being Paraplex G60. In practice a mixture of severalplasticizers will almost invariably be used.

I have found that superior results are achieved when the plasticizercomprises a major proportion of octyl diphenyl phosphate. For somereason, not now known to me, this particular plasticizer gives a foamedproduct having an unusually low density. In fact, -by using aplasticizer containing more than 50% of this compound, I can makeproducts having a density substantially lower than 500 grams per liter.Y

The relative amounts of resin and plasticizer can vary widely dependingupon many factors. As will be obvious, the amount of plasticizer shouldbe such as `to form a solid material after fusion of the resin andplasticizer. This solid material should have suflicient strength tocause the final cellular product to adequately resist conditionsencountered in normal service. Typically the amount of plasticizer willrange from 50 to 400 parts per 100 parts of resin. More commonly, I willemploy from 100 to 150 parts of plasticizer per 100 parts of resin.

Examples of the non-ionic surface-active agents that can be used in myinvention are:

1) Monoethers of polyglycols with long-chain fatty alcohols, such asreaction products of ethylene oxide or polyethylene glycol with along-chain fatty alcohol (e..g. the reaction product of ethylene oxideand oleyl` alcohol, viz., C'18H'35-('OC2H4)OH where n is 10 to 20)'.

(2) Monoesters of polyglycols with long-chain fatty acids,A such asreaction products of ethylene oxide or polyethylene glycol with along-chain fatty acidv (e. g. reaction-product of ethylene oxide orpolyethylene glycol with` oleic acid, viz.,

where-n is l to 20). An example of such a material is Emulphor ELA.

(3) Monoethers of polyglyeols with alkylated phenols, such as reactionproducts of ethylene oxide or polyethylene glycol withan alkyl phenol(e. g. reaction product of ethylene oxide and isopropyl phenol, viz.,

where n is l0 to 20).

(4) Partial esters of polyhydric alcohols with longchain monocarboxylic(fatty and/or resin) acids (e. g. glycerol monostearate, sorbitantrioleate).

The amount of the non-ionic surface-active agent is preferably equal tofrom 1 to 25 parts by weight based on 100 parts of the vinyl resin. Ihave obtained very good results using approximately 5.9 parts of thesurfaceactive agent per 100 parts of resin.

The alkali metal salts of sulfonated fatty alcohols are well-knownmaterials. These materials are often termed alkyl sulfates of eight toeighteen or more carbon atoms. They are also often called sulfatedalcohols, their manufacture being described on pages 53-66 of SurfaceActive Agents by Schwartz and Perry, published 1949 by IntersciencePublishers. Examples are sodium oleyl sulfate and sodium dodecyl (orlauryl) sulfate. Examples of commercial forms of the latter are DuponolWA and Duponol ME. I usually employ the sodium salt of the sulfo-natedfatty alcohol. The amount of this ingredient can range from 3 to 100parts per 100 parts of resin. proximately 29.4 parts of Duponol WA per100 parts of resin.

The alkali metal salts of ethylene diamine tetraacetic acid are alsowell-known materials. Usually I employ the sodium salts. I prefer to usethose salts containing at least two atoms of alkali metals per molecule.In other words I prefer to employ the di, trior tetra-alkali metal saltsof ethylene diamine tetraacetic acid. An eX- ample of a suitable salt isthat sold commercially as Nullapon BFC. Other examples are the materialssold under the trade name Sequestrene by the Alrose Chemical Co. ofProvidence, Rhode Island. I have obtained very good results usingfSequestrene NAZ (the technicallyY pure disodium salt, the dihy'drate),Sequestrene NA3 (the technically pure trisodium salt, the monohydrate),Sequestrene NAA (the technically pure tetrasodium salt, themonohydrate), and Sequestrene ST (the technical tetrasodium salt in theform of an 80% powder). I prefer to use the solid alkali. metal salts ofethylene diamine tetraacetic acid and I believe that the more nearlyanhydrous the salts are, the better the results.

The amount of the alkali metal salt of ethylene diamine tetraacetic acidcan range from 1 to 25 parts per 100 parts of resin. I have obtainedvery good results using approximately 5.9 parts.

I have obtained very good results using ap- Following preparation of auniform mixture of the plastisol and the foregoing three ingredients,this mixture is mechanically frothed in any suitable way so as toincorporate the surrounding gas, almost invariably air, into the mixtureand form a self-supporting, long-lasting froth. This step may beperformed in a manner similar to that by which air is beaten into arubber latex compound in the manufacture of latex foam rubber. Theamount of air incorporated in the mixture in this step can vary widelydepending upon the density desired of the final product. Since the frothretains substantially all of the incorporated air during the subsequentheating step, it is readily possible to control the density of the iinalproduct by controlling the amount of air incorporated in the frothingstep. Usually I incorporate sufficient air to give a nal product havinga density not over 700 grams per liter.

Following the frothing step, the resulting froth is shaped tothel formdesired in the final article.4 For example, it can be poured into asuitable form or it can be continuously fed onto a belt carrying itthrough a heating zone to form continuous at stock.

The shaped mixture is heated in any suitable way, as in a hot air oven,to fuse the resin and plasticizer into a single phase. The temperatureand time of heating should of course be such as to effect completefusion of the resin particles and the plasticizer. No specialprecautions have to be observed in order to prevent collapse of thesponge during this heating step. I prefer to employa temperature of from300 to 350 F. and a time ranging from 60 minutes at the lowertemperature to 10'minutes at the higher temperature. The heating step isconducted at atmospheric pressure.

The resulting fused sponge is then cooled down to room temperature, i.e., 100 F. or lower, whereuponit is ready for use.

The following examples illustrate my invention more fully. All partsexpressed in this specification and in the appended claims are byweight.

The following basic plastisol composition was used inthe examples:

Parts Vinyl resin (copolymer of vinyl chloride-5% vinyl acetate) .lPlasticizer (octyl diphenyl phosphate) 139 Stabilizer (dibasic leadphosphite) 6.6

Other vinyl resins, other plasticizers, and other stabilizers for vinylresins, may be substituted for the foregoing with equivalent results.

Examples I to 5 Example 1 2 3 4 5 Emulpllol' ELA 5. 9 5. 9 5. 9 5. 9 5.9 Duponol WA 29. 4 29. fl 29. 4 29. 4 29. 4 Nullapon BFC 5.

"Sequestreno NA'2 Sequestrene NA3 Sequestrene N A4 Seouestrene STOriginal density of mixture,

before frothing, grains/ Y p 'ter 1, 050 1, G60 1,110 1, 120 1,130VDensity of final sponge,

grams/liter; 505 515 525 490 450' In each case, the product had a tine,uniform pore structure, an attractive white appearance, and excellentcompressibility and resilience.

Examples 6 to I4 from 1 to 25 parts of a non-ionic surface-active agent,from 3 to 100 parts of an alkali metal salt of a sulfonated fatty acid,and from l to 25 parts of an alkali metal salt of ethylene diaminetetraacetic acid, and thereby 5 incorporating a surrounding gas in saidmixture, subse- Using the same basic formulation and technique asquently heating the resulting froth at a temperature and described inExamples 1 '[0 5, the effeCt 0f omitting One, for a time suflicient tofuse the resin particles with said two or all three of the extraneousingredients in accordplasticizer while maintaining the froth structure,and ance with my invention was determined. The amounts cooling theresulting material to room temperature. of added ingredients and thedensity data were as follows: 2. The process of claim l, wherein saidnon-ionic Example e 7 s 9 10 11 12 13 14 Emulphor ELA 5 5 5 5 5 "DuponolWA-- 25 25 25 25 Nullapon BFG 5 5 5 5 Sequestrene ST 5 Original Density1,080 1, 090 1,110 1,110 1,160 1,125 1,100 1,070 Density of lnal sponge1,050 1,090 1,070 980 515 1,130 930 1,() 525 It will be seen (Example 6)that omission of all three 20 surface-active agent is a monoester of apolyglycol with extraneous ingredients results in no lowering ofdensity; along-chain fatty acid. that omission of any two of the threeextraneous ingre- 3. The process of claim 1 wherein said surface-activedients results in no or only very slight lowering of density agent is amonoester of a polyglycol with a long-chain (Examples 7 to 9); and thatomission of any one of fatty acid, wherein said alkali metal salt of asulfonated the three extraneous ingredients results in no or only 25fatty alcohol is sodium lauryl sulfate, and wherein said very slightlowering of density (Examples 11 to 13). In alkali metal salt ofethylene diamine tetraacetic acid is contrast (Examples 10 and 14), useof all three inthe tetrasodium salt. gredients gives a remarkablelowering in density. 4. The process of claim l wherein the amount of gasFrom the foregoing, it will be seen that the present incorporated in themixture in the frothing step is such .invention provides a simple yeteffective process of as to give a product having a density of not over700 economically making plasticized vinyl resin sponge. The grams perliter. process of my invention is much cheaper than using a 5. Theprocess of making a plasticized vinyl resin chemical blowing agent. Itis also much cheaper than sponge which comprises mechanically frothingan intiexternal gassing of the plastisol with an inert gas such matemixture of approximately: 100 parts of particulate as carbon dioxideunder high pressure as taught for thermoplastic vinyl resin selectedfrom the group consistexample in Schwencke U. S. Patent No. 2,666,036,issued ing of polyvinyl chloride, vinyl chloride-vinyl acetate co-January 12, 1954. By means of my invention, it is polymer, vinylchloride-vinylidene chloride copolymer, readily possible to control thedensity of the final product vinyl chloride-diethyl maleate copolymer,and vinyl chlowithin wide limits by simply controlling the amount ofride-diethyl fumarate copolymer, the relative proportions airincorporated in the frothing step. Numerous other of combined monomersin the said copolymers being advantages of my invention will more fullyhereinafter equal to 85-95% of vinyl chloride and 15-5% of the appear.other stated monomer, 138 parts of octyl diphenyl phos- 'Having thusdescribed my invention, what I claim and phate, 5.9 parts of a monoesterof a polyglycol with a desire to protect by Letters Patent is:long-chain fatty acid, 29.4 parts of sodium lauryl sulfate, 1. Theprocess of making a plasticized vinyl resin 5.9 parts of the tetrasodiumsalt of ethylene diamine sponge which comprises mechanically frothing anintitetraacetic acid, and thereby incorporating the surroundmate mixtureof a plastisol comprising 100 parts of a ing gas in said mixture,subsequently heating the resultparticulate thermoplastic vinyl resinselected from the ing ,froth at a temperature and for a time suflicientto group consisting of polyvinyl chloride, vinyl chloridefuse theparticulate vinyl resin with said octyl diphenyl vinyl acetatecopolymer, vinyl chloride-vinylidene chlophosphate while maintaining thefroth structure, and ride copolymer, vinyl chloride-diethyl maleatecopolycooling the resulting material to room temperature. mer, and vinylchloride-diethyl fumarate, the relative 5 The PTOCeSS 0f Claim 5 whereinthe amount 0f proportions of combined monomers in the said copolygasUCOIPOIIX1 ill the IUXUF@ in the f othflg Step S mers being equal to-95% of vinyl chloride and 15-5 55 Such as t0 give a Product havmg adensly of not Ove-1' ofthe other stated monomer, and from 50 to 400parts of a high boiling organic liquid plasticizer for said resin,

700 grams per liter.

No references cited.

1. THE PROCESS OF MAKING A PLASTICIZED VINYL RESIN SPONGE WHICHCOMPRISES MECHANICALLY FROTHING AN INTIMATE MIXTURE OF A PASTISOLCOMPRISING 100 PARTS OF A PARTICULATE THERMOPLASTIC VINYL RESIN SELECTEDFROM THE GROUP CONSISTING OF POLYVINYL CHLORIDE, VINYL CHLORIDERIDECOPOLYMER, VINYL CHLORIDE-DIETHYL MELATE COPOLYMER, AND VINYLCHLORIDE-DIETHYL FUMARATE, THE RELATIVE PROPORTIONS OF COMBINED MONOMERSIN THE SAID COPOLYMERS BEING EQUAL TO 85-95% OF VINYL CHLORIDE AND 15-5%OF THE OTHER STATE MONOMER, AND FROM 50 TO 400 PARTS OF A HIGH BOILINGORGANIC LIQUID PLASTICIZER FOR SAID RESIN, FROM 1 TO 25 PARTS OF ANON-IONIC SURFACE-ACTIVE AGENT, FROM 3 TO 100 PARTS OF AN ALKALI METALSALT OF A SULFONATED FATTY ACID, AND FROM 1 TO 25 PARTS OF AN ALKALIMETAL SALT OF ETHYLENE DIAMINE TETRAACETIC ACID, AND THEREBYINCORPORATING A SURROUNDING GAS IN SAID MIXTURE, SUBSEQUENTLY HEATINGTHE RESULTING FROTH AT A TEMPERATURE AND FOR A TIME SUFFICIENT TO FUSETHE RESIN PARTICLES WITH SAID PLASTICIZER WHILE MAINTAINING THE FROTHSTRUCTURE, AND COOLING THE RESULTING MATERIAL TO ROOM TEMPERTURE.